This invention relates to fluorine-substituted hydrocarbon compounds, their production, and their use for cleaning solid surfaces, and more particularly to polyfluoropentanes, polyfluorohexanes, and polyfluoroheptanes, their production by the reduction of polyfluoroolefin starting materials, and their use as solvents.
Various organic solvents have been used as cleaning liquids for the removal of contaminants from contaminated articles and materials. Certain fluorine-containing organic compounds such as 1,1,2-trichloro-1,2,2-trifluoroethane have been reported as useful for this purpose, particularly with regard to cleaning organic polymers and plastics which may be sensitive to other more common and more powerful solvents such as trichloroethylene or perchloroethylene. Recently, however, there have been efforts to reduce the use of certain compounds such as trichlorotrifluoroethane which also contain chlorine because of a concern over their potential to deplete ozone, and to thereby affect the layer of ozone that is considered important in protecting the earth""s surface from ultraviolet radiation.
Boiling point, flammability and solvent power can often be adjusted by preparing mixtures of solvents. For example, certain mixtures of 1,1,2,-trichloro-1,2,2-trifluoroethane with other solvents (e.g., isopropanol and nitromethane) have been reported as useful in removing contaminants which are not removed by 1,1,2-trichloro-1,2,2-trifluoroethane alone, and in cleaning articles such as electronic circuit boards where the requirements for a cleaning solvent are relatively stringent, (i.e., it is generally desirable in circuit board cleaning to use solvents which have low boiling points, are non-flammable, have low toxicity, and have high solvent power so that flux such as rosin and flux residues which result from soldering electronic components to the circuit board can be removed without damage to the circuit board substrate).
While boiling, flammability, and solvent power can often be adjusted by preparing mixtures of solvents, the utility of the resulting mixtures can be limited for certain applications because the mixtures fractionate to an undesirable degree during use. Mixtures can also fractionate during recovery, making it more difficult to recover a solvent mixture with the original composition. Azeotropic compositions, with their constant boiling and constant composition characteristics, are thus considered-particularly useful.
Azeotropic compositions exhibit either a maximum or minimum boiling point and do not fractionate upon boiling. These characteristics are also important in the use of the solvent compositions in certain cleaning operations, such as removing solder fluxes and flux residues from printed circuit boards. Preferential evaporation of the more volatile components of the solvent mixtures, which would be the case if the mixtures were not azeotropes, or azeotrope-like, would result in mixtures with changed compositions which may have less desirable properties (e.g., lower solvency for contaminants such as rosin fluxes and/or less inertness toward the substrates such as electrical components).
Azeotropic characteristics are also desirable in vapor degreasing operations where redistilled material is isually used for final rinse-cleaning. Thus, the vapor defluxing or degreasing system acts as a still. Unless the solvent composition exhibits a constant boiling point (i.e., is an azeotrope or is azeotrope-like) fractionation will occur and undesirable solvent distribution may act to upset the safety and effectiveness of the cleaning operation.
A number of azeotropic compositions based upon halohydrocarbons containing fluorine have been discovered and in some cases used as solvents for the removal of solder fluxes and flux residues from printed circuit boards and for miscellaneous vapor degreasing applications. For example, U.S. Pat. No. 2,999,815 discloses the azeotrope of 1,1,2-trichloro-1,2,2-trifluoroethane with acetone; U.S. Pat. No. 3,903,009 discloses a ternary azeotrope of 1,1,2-trichloro-1,2,2-trifluoroethane with nitromethane and ethanol; U.S. Pat. No. 3,573,213 discloses an azeotrope of 1,1,2-trichloro-1,2,2-trifluoroethane with nitromethane; U.S. Pat. No. 3,789,006 discloses the ternary azeotrope of 1,1,2-trichloro-1,2,2-trifluoroethane with nitromethane and isopropanol; U.S. Pat. No. 3,728,268 discloses the ternary azeotrope of 1,1,2-trichloro-1,2,2-trifluoroethane with acetone and ethanol; U.S. Pat. No. 2,999,817 discloses the binary azeotrope of 1,1,2-trichloro-1,2,2-trifluoroethane and methylene chloride (i.e., dichloromethane); and U.S. Pat. No. 4,715,900 discloses ternary compositions of trichlorotrifluoroethane, dichlorodifluoroethane, and ethanol or methanol.
As noted above, many solvent compositions which have proven useful for cleaning contain at least one component which is a halogen-substituted hydrocarbon containing chlorine, and there have been concerns raised over the ozone depletion potential of halogen-substituted hydrocarbons which contain chlorine. Efforts are being made to develop compositions which may at least partially replace the chlorine containing components with other components having lower potential for ozone depletion. Azeotropic compositions of this type are of particular interest.
Means of synthesizing various fluorine-substituted alkanes have been reported.
U.S. Pat. No. 2,550,953 discloses catalytic hydrogenation of unsaturated fluorohydrocarbons.
U.S. Pat. No. 2,844,636 discloses that 1,1,2,3,4,4-hexafluorobutene can be made by reacting perfluorocyclobutene with hydrogen, using elemental iodine as the catalyst.
V. A. Grinberg et al., Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science, 988 (1979) report the synthesis of 3,4-dihydro perfluorohexane, CF3CF2CHFCHFCF2CF3, by the electrochemical reaction of trifluoroacetic acid, sodium trifluoroacetate and trifluoroethylene in aqueous acetonitrile as 5% of a three-component mixture that was isolated in 30% of the theoretical (based on current) amount.
V. F. Snegirev et al., Izvestiya Akademii Nauk SSSR, Ser ya Khimicheskaya, 1983, No 12, pp. 2775-2781, report the reduction of the branched perfluoroolefins, perfluoro-4-methyl-2-pentene and perfluoro-2-methyl-2-pentene to mono-, di- and trihydro derivatives by metal hydride complexes or by hydrogenation over a palladium/carbon catalyst.
J. Li et al., Youji Huaxue, 1984, 40-2, p. 24, report the palladium on alumina catalyzed hydrogenation of hexafluoropropylene dimers to give dihydro and trihydro reduction products.
I. L. Knunyants et al., Izvestiya Akademii Nauk SSSR, Otdelenie Khimicheskikh Nauk, 1960, No 8, pp. 1412-1418 discusses the catalytic hydrogenation of perfluoroethylene, propene and butenes.
U. S. Pat. No. 4,902,839 discloses certain tetrahydro derivatives of perfluorobutanes, perfluoropentanes and perfluorohexanes, as well as processes for their preparation.
In accordance with this invention, novel compounds are provided which contain no chlorine and which may be used alone or in combination with other miscible solvents (e.g., alcohols, ethers, esters, ketones, nitrogen-containing organic compounds such as acetonitrile and nitromethane, and halogenated hydrocarbons) as agents for cleaning solid surfaces.
The novel compounds of this invention include the group of linear dihydro and trihydro polyfluoropentanes, polyfluorohexanes and polyfluoroheptanes represented by the structural formulae CF3CHFCHFCF2CF3, CF3CH2CHFCF2CF3, CF3CHFCH2CF2CF3, CF3CHFCHFCF2CF2CF3, CF3CH2CHFCF2CF2CF2, CF3CHFCH2CF2CF2CF3, CF3CF2CH2CHFCF2CF3, CF3CF2CHFCHFCF2CF2CF3, CF3CHFCHFCF2CF2CF2CF3, CF3CHFCH2CF2CF2CF2CF3, CF3CH2CHFCF2CF2CF2CF3, CF3CF2CHFCH2CF2CF2CF3, and CF3CF2CH2CHFCF2CF2CF3.
A process is provided in accordance with this invention for preparing a linear trihydropolyfluoroalkane selected from the group consisting of CF3CH2CHFCF2CF3, CF3CHFCH2CF2CF3, CF3CH2CHFCF2CF2CF3, CF3CHFCH2CF2CF2CF3, CF3CF2CH2CHFCF2CF3, CF3CHFCH2CF2CF2CF2CF3, CF3CH2CHFCF2CF2CF2CF3, CF3CF2CHFCH2CF2CF2CF3, and CF3CF2CH2CHFCF2CF2CF3, which comprises the step of reacting an olefinic starting material in the liquid phase with hydrogen over a Group VIII metal catalyst (preferably in the presence of a polar solvent); wherein said olefinic starting material has the same number of carbon atoms as said trihydropolyfluoroalkane and is selected from the group of perfluoroolefins consisting of CF3CFxe2x95x90CFCF2CF3, CF3CFxe2x95x90CFCF2CF2CF3, CF3CF2CFxe2x95x90CFCF2CF3, CF3CF2CFxe2x95x90CFCF2CF2CF3, and CF3CFxe2x95x90CFCF2CF2CF2CF3; and wherein said olefinic starting material has its olefinic bond between the carbon atoms which correspond to the carbons which bear the hydrogen in said trihydropolyfluoroalkane.
Another process is provided in accordance with this invention for preparing a linear trihydropolyfluoroalkane selected from the group consisting of CF3CH2CHFCF2CF3, CF3CHFCH2CF2CF3, CF3CH2CHFCF2CF2CF3, CF3CHFCH2CF2CF2CF3, CF3CF2CH2CHFCF2CF3, CF3CHFCH2CF2CF2CF2CF3, CF3CH2CHFCF2CF2CF2CF3, CF3CF2CHFCH2CF2CF2CF3, and CF3CF2CH2CHFCF2CF2CF3, which comprises the step of reacting an olefinic starting material at an elevated temperature with hydrogen in the presence of at least one material selected from the group consisting of iodine and hydrogen iodide or with hydrogen iodide; wherein said olefinic starting material has the same number of carbon atoms as said trihydropolyfluoroalkane and is selected from the group consisting of CF3CHxe2x95x90CFCF2CF3, CF3CFxe2x95x90CHCF2CF3, CF3CHxe2x95x90CFCF2CF2CF3, CF3CFxe2x95x90CHCF2CF2CF3, CF3CF2CHxe2x95x90CFCF2CF3, CF3CF2CHxe2x95x90CFCF2CF2CF3, CF3CF2CFxe2x95x90CHCF2CF2CF3, CF3CHxe2x95x90CFCF2CF2CF2CF3, and CF3CFxe2x95x90CHCF2CF2CF2CF3; and wherein said olefinic starting material has its olefinic bond between the carbon atoms which correspond to the carbons which bear the hydrogen in said trihydropolyfluoroalkane.
In accordance with this invention a process is also provided for preparing a linear dihydropolyfluoroalkane selected from the group consisting of CF3CHFCHFCF2CF3, CF3CHFCHFCF2CF2CF3, CF3CF2CHFCHFCF2CF2CF3, CF3CHFCHFCF2CF2CF2CF3, and CF3CF2CHFCHFCF2CF3, which comprises the step of reacting an olefinic starting material in the vapor phase with hydrogen over a Group VIII metal catalyst; wherein said olefinic starting material has the same number of carbon atoms as said dihydropolyfluoroalkane and is selected from the group consisting of CF3CFxe2x95x90CFCF2CF3, CF3CFxe2x95x90CFCF2CF2CF3, CF3CF2CFxe2x95x90CFCF2CF3, CF3CF2CFxe2x95x90CFCF2CF2CF3, and CF3CFxe2x95x90CFCF2CF2CF2CF3; and wherein said olefinic starting material has its olefinic bond between the carbon atoms which correspond to the carbons which bear the hydrogen in said dihydropolyfluoroalkane.
Another process is provided in accordance with this invention for preparing a linear dihydropolyfluoroalkane selected from the group consisting of CF3CHFCHFCF2CF3, CF3CHFCHFCF2CF2CF3, CF3CF2CHFCHFCF2CF2CF3, CF3CHFCHFCF2CF2CF2CF3, and CF3CF2CHFCHFCF2CF3, which comprises the step of reacting an olefinic starting material in the liquid phase with hydrogen over a Group VIII metal catalyst (preferably in the absence of a polar solvent); wherein said olefinic starting material has the same number of carbon atoms as said dihydropolyfluoroalkane and is selected from the group consisting of CF3CFxe2x95x90CFCF2CF3, CF3CFxe2x95x90CFCF2CF2CF3, CF3CF2CFxe2x95x90CFCF2CF3, CF3CF2CFxe2x95x90CFCF2CF2CF3, and CF3CFxe2x95x90CFCF2CF2CF2CF3; and wherein said olefinic starting material has its olefinic bond between the carbon atoms which correspond to the carbons which bear the hydrogen in said dihydropolyfluoroalkane.
A third process is provided in accordance with this invention for preparing a linear dihydropolyfluoroalkane selected from the group consisting of CF3CHFCHFCF2CF3, CF3CHFCHFCF2CF2CF3, CF3CF2CHFCHFCF2CF2CF3, CF3CHFCHFCF2CF2CF2CF3, and CF3CF2CHFCHFCF2CF3, which comprises the step of reacting an olefinic starting material at an elevated temperature with hydrogen in the presence of at least one material selected from the group consisting of iodine and hydrogen iodide or with hydrogen iodide; wherein said olefinic starting material has the same number of carbon atoms as said dihydropolyfluoroalkane and is selected from the group consisting of CF3CFxe2x95x90CFCF2CF3, CF3CFxe2x95x90CFCF2CF2CF3, CF3CF2CFxe2x95x90CFCF2CF3, CF3CF2CFxe2x95x90CFCF2CF2CF3, and CF3CFxe2x95x90CFCF2CF2CF2CF3; and wherein said olefinic starting material has its olefinic bond between the carbon atoms which correspond to the carbons which bear the hydrogen in said dihydropolyfluoroalkane.
This invention provides novel saturated linear polyfluorohydrocarbons (i.e., polyfluoroalkanes) which contain two or three hydrogen atoms per molecule. The trihydropolyfluoroalkanes of this invention include the trihydropolyfluoropentanes represented by the structural formulae CF3CH2CHFCF2CF3 and CF3CHFCH2CF2CF3; the trihydropolyfluorohexanes represented by the structural formulae CF3CH2CHFCF2CF2CF3, CF3CHFCH2CF2CF2CF3, and CF3CF2CH2CHFCF2CF3; and the trihydropolyfluoroheptanes represented by the structural formulae CF3CHFCH2CF2CF2CF2CF3, CF3CH2CHFCF2CF2CF2CF3, CF3CF2CHFCH2CF2CF2CF3, and CF3CF2CH2CHFCF2CF2CF3.
A process is provided in accordance with this invention for preparing these trihydropolyfluoroalkanes which comprises the step of reacting an olefinic starting material in the liquid phase with hydrogen over a Group VIII metal catalyst, preferably from the palladium group (i.e., Pd, Rh and/or Ru). Palladium and rhodium are the more preferred metals, with palladium being most preferred. The metal catalyst may be supported, for example on carbon or on alumina. The olefinic starting material used for this process has the same number of carbon atoms as the desired trihydropolyfluoroalkane and is selected from the group of perfluoroolefins consisting of CF3CFxe2x95x90CFCF2CF3, CF3CFxe2x95x90CFCF2CF2CF3, CF3CF2CFxe2x95x90CFCF2CF3, CF3CF2CFxe2x95x90CFCF2CF2CF3, and CF3CFxe2x95x90CFCF2CF2CF2CF3. Thus, a polyfluoroalkane selected from the group consisting of CF3CH2CHFCF2CF3 and CF3CHFCH2CF2CF3 can be produced by hydrogenating CF3CFxe2x95x90CFCF2CF3 over a metal catalyst in accordance with this invention; a polyfluoroalkane selected from the group consisting of CF3CH2CHFCF2CF2CF3, CF3CHFCH2CF2CF2CF3, and CF3CF2CH2CHFCF2CF3 can be produced by hydrogenating a starting material selected from the group consisting of CF3CFxe2x95x90CFCF2CF2CF3 and CF3CF2CFxe2x95x90CFCF2CF3 over a metal catalyst in accordance with this invention; and a polyfluoroalkane selected from the group consisting of CF3CHFCH2CF2CF2CF2CF3, CF3CH2CHFCF2CF2CF2CF3, CF3CF2CHFCH2CF2CF2CF3 and CF3CF2CH2CHFCF2CF2CF3 can be produced by hydrogenating a starting material selected from the group consisting of CF3CF2CFxe2x95x90CFCF2CF2CF3 and CF3CFxe2x95x90CFCF2CF2CF2CF3 over a metal catalyst in accordance with this invention. In any case the olefinic starting material should have its olefinic bond between the carbon atoms which correspond to the carbons which bear the hydrogen in the desired trihydropolyfluoroalkane.
The reduction can be carried out at temperatures in the range of from about 0xc2x0 C. to about 200xc2x0 C. The preferred temperature range is from about 25xc2x0 C. to about 100xc2x0 C. The pressure of the hydrogenation may be within a wide range, from less than 1 atmosphere to extremely high pressures, but normally pressures from 1 atmosphere to about 10 atmospheres is preferred. The molar ratio of hydrogen to olefinic starting material for this process is preferably between about 1:1 and 100:1; and is more preferably between about 2:1 and 10:1. For batch processes, the hydrogen may be provided by continuous or intermittent addition to a reactor containing the olefinic starting material and the catalyst until the desired ratio (based upon the initial amount of starting material) is attained.
The hydrogenation is preferably conducted in the presence of a polar solvent. The presence of a polar solvent is essential for high selectivity to the trihydro derivatives from the perfluoroolefin starting materials. Suitable polar solvents which may be employed include water, alcohols, glycol, acetic acid, dimethylformamide, N-methyl pyrollidone and triethylamine, or mixtures thereof. Methanol is a preferred polar solvent.
The olefinic starting materials for this process may be prepared in accordance with the teachings of U.S. patent application Ser. No. 07/595,839 (see U.S. Pat. No. 5,162,594 which issued pursuant to a continuation-in-part thereof), which is hereby incorporated by reference in its entirety. According to the teachings therein, polyfluoroolefins having at least 5 carbon atoms may be manufactured by reacting together two selected polyfluoroolefins in the presence of a catalyst of the formula AlX3 where X is one or more of F, Cl or Br (provided that X is not entirely F). As exemplified by Example A herein, a five carbon perfluoroolefinic starting material may be prepared by the reaction of hexafluoropropene (HFP) with tetrafluoroethylene (TFE). Six carbon perfluoro-olefinic starting materials may be prepared by the reaction, substantially according to the procedure of Example A, of 1,1,1,4,4,4-hexafluoro-2,3-dichloro-2-butene with TFE to yield an intermediate product comprising perfluoro-2,3-dichloro-2-hexene which may then be converted to a mixture of perfluoro-2-hexene and perfluoro-3-hexene by reaction with potassium fluoride in refluxing N-methyl pyrolidone. A mixture of seven carbon perfluoroolefinic starting materials may be prepared by the reaction, substantially according to the procedure of Example A, of hexafluoro-propene with 2 moles of TFE.
Another process is provided in accordance with this invention for preparing a linear trihydropolyfluoroalkane selected from the group consisting of CF3CH2CHFCF2CF3, CF3CHFCH2CF2CF3, CF3CH2CHFCF2CF2CF3, CF3CHFCH2CF2CF2CF3, CF3CF2CH2CHFCF2CF3, CF3CHFCH2CF2CF2CF2CF3, CF3CH2CHFCF2CF2CF2CF3, CF3CF2CHFCH2CF2CF2CF3, and CF3CF2CH2CHFCF2CF2CF3, which comprises the step of reacting an olefinic starting material at an elevated temperature with hydrogen in the presence of at least one material selected from the group consisting of iodine and hydrogen iodide or with hydrogen iodide; wherein said olefinic starting material has the same number of carbon atoms as said trihydropolyfluoroalkane and is selected from the group consisting of CF3CHxe2x95x90CFCF2CF3, CF3CFxe2x95x90CHCF2CF3, CF3CHxe2x95x90CFCF2CF2CF3, CF3CFxe2x95x90CHCF2CF2CF3, CF3CF2CHxe2x95x90CFCF2CF3, CF3CF2CHxe2x95x90CFCF2CF2CF3, CF3CF2CFxe2x95x90CHCF2CF2CF3, CF3CHxe2x95x90CFCF2CF2CF2CF3, and CF3CFxe2x95x90CHCF2CF2CF2CF3; and wherein said olefinic starting material has its olefinic bond between the carbon atoms which correspond to the carbons which bear the hydrogen in said trihydropolyfluoroalkane. The hydrogen-containing olefinic starting materials may be made substantially according to the procedure of Example A, but using monohydro compounds rather than perfluoro compounds (e.g., 2H-pentafluoropropene rather than HFP).
Iodine and/or HI is used for this hydrogenation in accordance with the teachings of U.S. patent application Ser. No. 07/533,333 (see U.S. Pat. No. 5,097,082 which issued pursuant to a continuation-in-part thereof). Hydrogen iodide for the reaction may be provided by several methods. For example, the reaction may be run with stoichiometric HI. Alternatively, the reaction may be run with catalytic amounts of HI in the presence of hydrogen. The reaction may also be run with hydrogen using catalytic amounts of iodine. This latter method is preferred for batch reactions and for ease of handling. This reaction may be accomplished in the absence of supported metal catalysts; and indeed the catalyst for this reaction typically consists essentially of iodine and/or hydrogen iodide. The reaction temperature for this reaction should generally be from 100xc2x0 C. to 500xc2x0 C. A preferred temperature range is from 200xc2x0 C. to 400xc2x0 C. This reaction may be run at a pressure of from about 50 psi to 5000 psi, with 500 psi to 1500 psi being preferred.
The amount of hydrogen provided for contact with the olefinic starting material (either by addition of HI or by feed of H2 gas) should represent at least one molecule of hydrogen for each olefinic bond to be saturated, and is preferably 10 times said minimum, or less (i.e., the molar ratio of hydrogen available for reacting to olefinic starting material is preferably between 10:1 and 1:1). When hydrogen gas is used, the hydrogen can be fed either in the pure state or diluted with an inert gas (e.g., nitrogen, helium or argon).
The dihydropolyfluoroalkanes of this invention include the dihydropolyfluoropentane represented by the structural formula CF3CHFCHFCF2CF3; the dihydropolyfluorohexane represented by the structural formula CF3CHFCHFCF2CF2CF3; and the dihydropolyfluoroheptanes represented by the structural formulae CF3CF2CHFCHFCF2CF2CF3 and CF3CHFCHFCF2CF2CF2CF3.
A process is provided in accordance with this invention for preparing a linear dihydropolyfluoroalkane selected from the group consisting of CF3CHFCHFCF2CF3, CF3CHFCHFCF2CF2CF3, CF3CF2CHFCHFCF2CF2CF3, CF3CHFCHFCF2CF2CF2CF3, and CF3CF2CHFCHFCF2CF3, which comprises the step of reacting an olefinic starting material in the vapor phase with hydrogen over a Group VIII metal catalyst. Preferably the catalyst is from the palladium group. The olefinic starting material for this process has the same number of carbon atoms as the desired dihydropolyfluoroalkanes and is selected from the group consisting of CF3CFxe2x95x90CFCF2CF3, CF3CFxe2x95x90CFCF2CF2CF3, CF3CF2CFxe2x95x90CFCF2CF3, CF3CF2CFxe2x95x90CFCF2CF2CF3, and CF3CFxe2x95x90CFCF2CF2CF2CF3; and has its olefinic bond between the carbon atoms which correspond to the carbons which bear the hydrogen in said dihydropolyfluoroalkane.
Unsupported metal catalysts and supported metal catalysts wherein the metal is palladium, rhodium, or ruthenium are particularly suitable for use in this process. Supports such as carbon or alumina may be employed. Supported palladium catalysts are preferred.
The vapor phase reduction can be carried out at temperatures in the range of from about 50xc2x0 C. to about 250xc2x0 C.; the preferred temperature range is from about 100xc2x0 C. to about 200xc2x0 C. The pressure of the hydrogenation may vary widely from less than 1 atmosphere to 20 or more atmospheres. The molar ratio of hydrogen to olefinic starting material for this process is preferably between about 0.5:1 and 4:1, and is more preferably between about 0.5:1 and 1.5:1.
Another process is provided in accordance with this invention for preparing a linear dihydropolyfluoroalkane selected from the group consisting of CF3CHFCHFCF2CF3, CF3CHFCHFCF2CF2CF3, CF3CF2CHFCHFCF2CF2CF3, CF3CHFCHFCF2CF2CF2CF3, and CF3CF2CHFCHFCF2CF3, which comprises the step of reacting an olefinic starting material in the liquid phase with hydrogen over a Group VIII metal catalyst (preferably from the palladium group); wherein said olefinic starting material has the same number of carbon atoms as said dihydropolyfluoroalkane and is selected from the group consisting of CF3CFxe2x95x90CFCF2CF3, CF3CFxe2x95x90CFCF2CF2CF3, CF3CF2CFxe2x95x90CFCF2CF3, CF3CF2CFxe2x95x90CFCF2CF2CF3, and CF3CFxe2x95x90CFCF2CF2CF2CF3; and wherein said olefinic starting material has its olefinic bond between the carbon atoms which correspond to the carbons which bear the hydrogen in said dihydropolyfluoroalkane.
Palladium and rhodium are the preferred metals, with palladium being the most preferred. The metal catalysts may be supported, for example, on carbon or on alumina, with carbon the preferred support.
The liquid phase reduction can be carried out at temperatures ranging from about 0xc2x0 C. to 200xc2x0 C., with a preferred range being from about 25xc2x0 C. to about 100xc2x0 C. The pressure of the hydrogenation may vary widely from less than 1 atmosphere to 30 atmospheres or more. The molar ratio of hydrogen to olefinic starting material for this process is preferably between about 1:1 and 100:1 and is more preferably between about 1:1 and 10:1.
This hydrogenation is preferably carried out in the absence of a polar solvent. The reduction may be carried out neat (i.e., using no solvent or diluent) or in the presence of a non-polar solvent. Suitable nonpolar solvents which may be employed include inert low dielectric alkanes (e.g., nonane and cyclohexane) or low dielectric aromatics (e.g., toluene, benzene and orthoxylene).
Another process is provided in accordance with this invention for preparing a linear dihydropolyfluoroalkane selected from the group consisting of CF3CHFCHFCF2CF3, CF3CHFCHFCF2CF2CF3, CF3CF2CHFCHFCF2CF2CF3, CF3CHFCHFCF2CF2CF2CF3, and CF3CF2CHFCHFCF2CF3, which comprises the step of reacting an olefinic starting material which has the same number of carbons as said dihydropolyfluoroalkane and is selected from the group consisting of CF3CFxe2x95x90CFCF2CF3, CF3CFxe2x95x90CFCF2CF2CF3, CF3CF2CFxe2x95x90CFCF2CF3, CF3CF2CFxe2x95x90CFCF2CF2CF3, and CF3CFxe2x95x90CFCF2CF2CF2CF3, at an elevated temperature with hydrogen in the presence of at least one material selected from the group consisting of iodine and hydrogen iodide or with hydrogen iodide. The olefinic starting material should have its olefinic bond between the carbon atoms which correspond to the carbons which bear the hydrogen in the desired dihydropolyfluoroalkane.
Iodine and/or HI is used for this hydrogenation in accordance with the teachings of U.S. patent application Ser. No. 07/533,333. Hydrogen iodide for the reaction may be provided by several methods. For example, the reaction may be run with stoichiometric HI. Alternatively, the reaction may be run with catalytic amounts of HI in the presence of hydrogen. The reaction may also be run with hydrogen using catalytic amounts of iodine. This latter method is preferred for batch reactions and for ease of handling. This reaction may be accomplished in the absence of supported metal catalysts; and indeed the catalyst for this reaction typically consists essentially of iodine and/or hydrogen iodide. The reaction temperature for this reaction should generally be from 100xc2x0 C. to 500xc2x0 C. A preferred temperature range is from 200xc2x0 C. to 400xc2x0 C. This reaction may be run at a pressure of from about 50 psi to 5000 psi, with 500 psi to 1500 psi being preferred.
The amount of hydrogen provided for contact with the olefinic starting material (either by addition of HI or by feed of H2 gas) should represent at least one molecule of hydrogen for each olefinic bond to be saturated, and is preferably 10 times said minimum, or less (i.e., the molar ratio of hydrogen available for reacting to olefinic starting material is preferably between 10:1 and 1:1). When hydrogen gas is used, the hydrogen can be fed either in the pure state or diluted with an inert gas (e.g., nitrogen, helium or argon).
The processes of this invention wherein the olefinic starting material is hydrogenated over a palladium group metal catalyst, allow for selecting between processes wherein the major product (i.e., above 50 mole percent based upon the amount of olefinic starting material hydrogenated) is a dihydropolyfluoroalkane, and processes wherein the major product is a trihydropolyfluoroalkane. In particular, liquid phase processes wherein polar solvents are used favor the production of trihydropolyfluoroalkanes and may thus be used to produce trihydropolyfluoroalkanes as the major product. In a preferred process, where high yield of trihydropolyfluoroalkanes is desired, a liquid phase process using polar solvents may be used to produce about 65 mole percent or more trihydropolyfluoroalkane product. Examples 1, 2, 4, 7, 10 and 15 herein are referenced as examples of trihydrononafluoropentane preparation.
On the other hand vapor phase processes, neat liquid phase processes, and liquid phase processes using non-polar solvents (i.e., processes essentially free of polar solvents) favor production of dihydropolyfluoroalkanes and may thus be used to produce dihydropolyfluoroalkanes as the major product of the reaction. In a preferred process, where high yield of dihydropolyfluoroalkanes is desired, a vapor phase process, a neat liquid process, or a liquid phase process using non-polar solvents may be used to produce about 65 mole percent or more dihydropolyfluoroalkane product. Examples 5, 6, 8, 9, 11, 12, 13 and 14 herein are referenced as examples of dihydropolyfluoroalkane preparation. Examples 13 and 14 indicate further that the use of an appropriate solvent can result in the formation of one diastereomeric dihydro compound selectively. Example 8 illustrates the high selectivity for introduction of two hydrogens which is possible in a vapor phase reaction using a palladium catalyst.
The processes of this invention which do not use metal catalysts and which react olefinic starting material with hydrogen in the presence of iodine and/or hydrogen iodide or with hydrogen iodide, allow for producing as the major product a polyfluoroalkane wherein exactly two hydrogens have been added to said olefinic starting material. In a preferred process, where high yield of polyfluoroalkane wherein exactly two hydrogens have been added to an olefinic starting material is desired, the processes using iodine and/or hydrogen iodide may be. used to produce about 95 mole percent or more of product wherein exactly two hydrogens have been added to the olefinic starting material. For example, 2,3-dihydrodecafluoropentane of over 99% purity can be obtained by the reaction of one part perfluoropentene-2 with excess hydrogen and about 0.5 part of iodine at 300xc2x0 C. and 1000 psi for 20 hours (see Example 3 herein).
The dihydro and trihydro linear polyfluoropentanes, polyfluorohexanes and polyfluoroheptanes of this invention are useful as solvents (especially those compounds having boiling points of 100xc2x0 C. or less). They are replacements for currently environmentally suspect chlorofluorocarbons such as trichlorotrifluoroethane. They have zero ozone depletion potential. They are non-flammable. These polyfluoroalkanes may be used by themselves or in combination with other miscible solvents as cleaning agents or defluxing agents for solid surfaces, for example, printed wire boards. The compounds having boiling points above 75xc2x0 C. are useful as vapor degreasers. The compounds of this invention may also be used as drying agents.
The dihydropolyfluoroalkanes and trihydropolyfluoroalkanes of this invention are miscible with various solvents conventionally used in cleaning operations. Compositions suitable for use in cleaning operations can be prepared which comprise a mixture of dihydro- and/or trihydropolyfluoroalkanes of this invention with one or more compounds selected from the group consisting of alcohols, ethers, esters, ketones, nitromethane, acetonitrile, and halogenated hydrocarbons. The preferred alcohols and halogenated hydrocarbons contain from 1 to 4 carbon atoms; the preferred ethers contain from 2 to 6 carbon atoms; and the preferred esters and ketones contain from 3 to 6 carbon atoms. Examples of suitable alcohols include methanol, ethanol and isopropanol. Examples of suitable ethers include tetrahydrofuran and diethylether. Examples of suitable ketones include acetone and methylethylketone. Examples of suitable halogenated hydrocarbons include methylene chloride (i.e., dichloromethane), 1,1,2-trichloro-1,2,2-trifluoroethane, dichlorodifluoroethane, trichloroethene, and trans-1,2-dichloroethylene. Preferably, such compositions contain at least about 5 percent by weight total of the polyfluoroalkanes of this invention; and can contain up to 99 percent by weight, or even more thereof. Preferred compositions include mixtures of CF3CHFCHFCF2CF3, CF3CH2CHFCF2CF3 or CF3CHFCH2CF2CF3 (especially CF3CHFCHFCF2CF3) with one or more of said alcohols, ethers, esters, ketones, nitromethane, acetonitrile and halogenated hydrocarbons. Most preferred with respect to ozone depletion potential are compositions in which no component contains chlorine.
The mixtures of this invention are useful in a wide variety of processes for cleaning solid surfaces which comprise treating said surface therewith. Applications include removal of flux and flux residues from printed circuit boards contaminated therewith.
Compositions which comprise an admixture of effective amounts of one or more of the dihydropolyfluoroalkanes and trihydropolyfluoroalkanes of this invention with one or more solvents selected from the group consisting of alcohols, ethers, esters, ketones, nitromethane, acetonitrile and halogenated hydrocarbons to form an azeotrope or azeotrope-like mixture are considered especially useful. Reference is made to U.S. patent application Ser. No. 07/595,833 (see U.S. Pat. No. 5,064,559 which issued pursuant thereto) and to U.S. patent application Ser. No. 07/595,834 (see U.S. Pat. No. 5,064,560 which issued pursuant thereto) for providing examples of certain azeotrope admixtures. In particular, azeotropic compositions consisting essentially of about 95.3 weight percent CF3CHFCHFCF2CF3 and about 4.7 weight percent methanol (boiling point about 39.9xc2x0 C.); consisting essentially of about 97.1 weight percent CF3CHFCHFCF2CF3 and about 2.9 weight percent ethanol (boiling point about 43.4xc2x0 C.); consisting essentially of about 97.4 weight percent CF3CHFCHFCF2CF3 and about 2.6 weight isopropanol (boiling point about 45.5xc2x0 C.); consisting essentially of about 60.5 weight percent CF3CHFCHFCF2CF3, about 36.2 weight percent trans 1,2-dichloroethylene, and about 3.3 weight percent methanol (boiling point about 35.3xc2x0 C.); and consisting essentially of about 63.9 weight percent CF3CHFCHFCF2CF3, about 35.1 weight percent trans 1,2-dichloroethylene and about 1.0 weight percent ethanol (boiling point about 35.1xc2x0 C.) are considered useful for cleaning printed circuit board contaminated with flux and flux-residues.
The compositions of the invention may be used in conventional apparatus, employing conventional operating techniques. The solvent(s) may be used without heat if desired, but the cleaning action of the solvent may be assisted by conventional means (e.g., heating, agitation, etc.). In some applications (e.g., removing certain tenacious fluxes from soldered components) it may be advantageous to use ultrasonic irradiation in combination with the solvent(s).
Compositions provided in accordance with this invention can be used in cleaning processes such as is described in U.S. Pat. No. 3,881,949 and U.S. Pat. No. 4,715,900, both of which are incorporated herein by reference.
The mixtures of the instant invention can be prepared by any convenient method including mixing or combining the desired amounts of the components. A preferred method is to weigh the desired amounts of each component and thereafter combine them in an appropriate container.